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New Sabaj a10h a Worthy Topping L30 Competitor?

escalibur

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So these copy-pastas were the actual reason for pre-2012 L30s? :D
 

liu

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Sabaj A10h, We have done a 8kV ESD test before send out, and passed it. Take it easy.

8kv is the standard test and nowhere near the real world scenarios. In the L30 case, pre-2012 model successfully passed 8kv but still failed in real world, and was recalled later. Read Jonh Yang's following two posts on their testing:

I have addressed this issue. But here we are.
In house testing and out sourced testing are different. Everything is tested for parameters and regulations before released. That's true.
But when we are talking about ESD problem in real world and reproduce it in our own lab. It's very different. The thing is from the regulation it only needs to pass 4kV to 8kV. When in real world it can go up to 20kV to 50kV.
And we have to understand these are not basic stuff. You can just ground the chassis and call it a day. But in some cases like this one is not that simple. To get to the end of this, it requires a lot of deeper knowledge and investigation. But on the other hand you can prevent this using some extra components willy nilly. But how many things are like this? You can't just foresee all the issue and just smash everything onto the board. That doesn't happen.
The main issue is not ESD but the potential harm to headphones. Preventing that from happening, and everything else don't really matter that much do they?


It's either isolated from earth or grounded at the input ground to upstream device.
If the voltage is too high the esd will discharge through the power supply. As it's low energy it won't cause any damage. And in our in house testing there's no failure with continuous 15KV pulses either condition.


following conclusions you can get from his statement:

1. pre-2012 models passed the standard testing (which is 4kv and 8kv). but those devices still damaged user's headphones.
2. the fixed version, with grounding and hp protection fix, can pass continuous 15kv spike -- i think it's the highest voltage their equipment can get

moreover, traditional 4kv-8kv esd tests are only there to proof your device is safe for human to use. it is not designed to show your device is immune to HP damage. You still need an effective hp protection circuit, to prevent not only esd, but also other kinds of damages, such as failed op amp.

I strongly suggest you test with 15kv continuous spike. if you can pass that test, maybe you can release as is. I just want to help you to prevent a potential recall.
 
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GGroch

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So this little amp has the remote to change the volume remotely? :p
I would think so, but the legend on the remote photo does not actually say that.
Sabajremote.jpg



ADD: Here is a link to the owners manual. The remote DOES control volume.
 

half_dog

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Not gonna lie, I'm curious about the A10d. Specific SE DAC with a -118dB SINAD. It seems to have a better noise floor than E30. Using IEM I can hear very very faint noise when there is no music with L30+E30 - my Galaxy S9 (S9>TRS to RCA>L30) is quieter, no noise at all. Maybe a defective E30?
 

Racheski

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Not gonna lie, I'm curious about the A10d. Specific SE DAC with a -118dB SINAD. It seems to have a better noise floor than E30. Using IEM I can hear very very faint noise when there is no music with L30+E30 - my Galaxy S9 (S9>TRS to RCA>L30) is quieter, no noise at all. Maybe a defective E30?
What you are describing is more likely a ground loop among the E30, L30, and power source. Are both the E30 and L30 plugged into the same power strip or wall power outlet?
 

half_dog

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What you are describing is more likely a ground loop among the E30, L30, and power source. Are both the E30 and L30 plugged into the same power strip or wall power outlet?
Thanks for your input. It can be ground loop, but...
Yes, they were plugged in the same power strip. Even when feeding E30 by S9 using an OTG cable I got the same noise. I did some measurements with a TASCAM US-366 connected to a notebook - the measurements were made on battery and with power plugged. Didn't get any 60Hz neither harmonics. I did it with other DACs as D10S, KTB (the loudest one), M500... This and E30 were the quiest ones, but still listenable. During normal usage the noise is completely irrelevant, but some times when I doing critical listening at night I can hear it. It's nothing that I can't live with, but I would like to try different DACs and see if they are less noisy. BTW, the noise is volume dependent, but most of the time L30 is at its max (0 gain) and I control the volume via software or remote control. And it reminds more a white noise than a 60Hz hum. I'm not gonna hate either dislike E30, it just something that call my attention :)
 

Human Bass

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Thanks for your input. It can be ground loop, but...
Yes, they were plugged in the same power strip. Even when feeding E30 by S9 using an OTG cable I got the same noise. I did some measurements with a TASCAM US-366 connected to a notebook - the measurements were made on battery and with power plugged. Didn't get any 60Hz neither harmonics. I did it with other DACs as D10S, KTB (the loudest one), M500... This and E30 were the quiest ones, but still listenable. During normal usage the noise is completely irrelevant, but some times when I doing critical listening at night I can hear it. It's nothing that I can't live with, but I would like to try different DACs and see if they are less noisy. BTW, the noise is volume dependent, but most of the time L30 is at its max (0 gain) and I control the volume via software or remote control. And it reminds more a white noise than a 60Hz hum. I'm not gonna hate either dislike E30, it just something that call my attention :)
It can also be radio noise captured by the rca cables. It happened to my d50s+a50s stack.
 

solderdude

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Sabaj A10h, We have done a 8kV ESD test before send out, and passed it. Take it easy.

Questions I have.

1: Is the enclosure connected to signal ground ?
2: It looks like the amp section is only TPA6120A and does not have the same audio circuit but does combine 2 TPA6120A 'halves' to increase current. This amp does not have the same opamp that blew up in the L30.
3: How come the specs don't match the power supply voltage (+/- 14V where the - voltage is created using a DCDC converter ?)
4: Is DC protection a separate circuit or governed by a small processor ?
5: It looks like only the DC protection circuit was a copy and the rest of the circuit, particularly the audio path, was not.
6: Is the audio path simply input>Relay volume control>TPA6120A>output or is there a buffer in front of the volume control ?
 

liu

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2: It looks like the amp section is only TPA6120A and does not have the same audio circuit but does combine 2 TPA6120A 'halves' to increase current. This amp does not have the same opamp that blew up in the L30.
no opa1612 is hidden below the relay board.
 
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solderdude

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The question is whether it is used as a buffer or integrated in the overall feedback loop.
Given the distance and speed of the used components and parts around the TPA6120A I would suspect it is used as a buffer or just have something to do with gain structures.

The higher input resistance, the distance from the TPA all suggest it is not an L30 with a different volume control and the given that the ESD issue is because of the low input resistance and direct path to the volpot shaft (which isn't the case in this amp) it is unlikely to suffer a similar fate or even have the same issue.
 
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liu

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The question is whether it is used as a buffer or integrated in the overall feedback loop.
Given the distance and speed of the used components and parts around the TPA6120A I would suspect it is used as a buffer or just have something to do with gain structures. I think the 1612 needs to be really close physically to the TPA for this to work.

The higher input resistance, the distance from the TPA all suggest it is not an L30 with a different volume control and the given that the ESD issue is because of the low input resistance and direct path to the volpot shaft (which isn't the case in this amp) it is unlikely to suffer a similar fate or even have the same issue.
it's the same as L30 --- nested feedback. it is very close to the tpa6120a2. you just can't see it --- it's below the daughter board.
 

solderdude

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Why the big difference in input impedance as that was key to low noise performance and the reason why the 1612 blew up with ESD pulses.
This is unlikely to happen with this amp.

Where did you read it was nested feedback ?
Do you happen to have this amp and if so can you take a picture ?
 
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GGroch

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Mine arrived yesterday. I have not listened yet, but initial observations:

1. Looks very nice in person. Everything fits well and the cast case looks like to have an attractive light powder coat, not smooth glossy.
2. I no longer have an L30 to compare, but width, height look identical, but it is longer and at 15 oz I think heavier.
3. Volume control has 100 one dB steps, -99 to zero. There are separate volume memories for Pre-and headphone outputs.
4. Short press on volume switches to control selection, then turn to select. In this order: gain (3 levels), then Preamp/Headphone Output, then LCD brightness (3 levels, no off). About 3 seconds after last press, the control returns to volume. The LCD remains illuminated with volume setting.
5. Long press on volume turns power off. Default is on when DC power is applied.
6. Included power supply is 15v 4A
7. Peterwen's new remote diagram is mostly right (thanks Peter), but the "A" and "B" buttons switch the remote code to control the A10a amp and A10d DAC...so if the remote does not work, hit "B". Nice feature if you have the stack.

I see there is a Sabaj a20 series being released with balanced connections among other differences.

I have offered the A10h to Amir for testing if he does not already have one on the way and fits into his schedule.
 
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